Methods for adaptively controlling lighting based upon traffic in an outdoor lighting network

ABSTRACT

Methods for an outdoor lighting network ( 100 ) are disclosed. The methods can adaptively control lighting requirements based upon traffic in the outdoor lighting network ( 100 ). The adaptive control provides illumination over a certain response range based upon detection of an object ( 20 ) and in addition possibly a velocity of the object ( 20 ) by a lighting unit (LUs 1-8) equipped with a sensor ( 12 ) For the outdoor lighting network ( 100 ), the disclosed methods include deciding when a control message should be transmitted to other lighting units (LUs 1-8), selecting one or more control messaging protocols with modes adapted to achieve a response range depending on the velocity of the object ( 20 ) and controlling behavior of a light level output of the lighting unit (LU 1-8).

CROSS-REFERENCE TO PRIOR APPLICATIONS

This application is the U.S. National Phase application under 35 U.S.C.§371 of International Application No. PCT/IB2013/053161, filed on Apr.22, 2013, which claims the benefit of U.S. Provisional PatentApplication No. 61/641,618, filed on May 2, 2012. These applications arehereby incorporated by reference herein.

The present invention relates to various methods and protocols foradaptive lighting in an outdoor lighting network, more particularly,methods to adaptively decide based upon traffic patterns on lightlevel/dimming requirements for outdoor lighting units that use decisionprotocols on when a control message should be transmitted and controlmessaging protocols with adaptive modes.

Outdoor lighting networks (OLNs) are increasingly becoming intelligent,with sensors, actuators and communication modules in lighting unit/poleinstallations that can respectively detect the presence of objects,control the dimming of luminaries, and communicate relevant controlinformation across the lighting system. Smart dimming strategies thatare adapted in accordance with object detection conditions can help inachieving energy efficiency. Light pollution is also reduced by dimmingselectively to ensure a certain response behavior as compared to asystem that has all lighting units/poles constantly on.

Conventional sensors, e.g., passive infrared (PIR) sensors, cameras, inthe OLN give out binary detection results. Such conventional sensors maysend a “detection” result if an object is detected within the sensingrange of the sensor. The sensor may also periodically attempt to detectobjects within the sensing range and if an object is detected, a“detect” results, or else a “no detection” results.

A conventional control protocol based on binary detection results worksas follows. Based upon a local detection or non-detection via a sensor,the lighting unit broadcasts a message periodically. A lamp at thelighting unit goes ON if it has a local detection or receives at leastone ON message in a received broadcast message from another lightingunit in the vicinity. The lamp goes OFF if it receives an OFF message inthe broadcast messages and has no local detection, or if a timerexpires. Such conventional protocols, while being simple, incur a largeerror rate in expected dimming behavior and also suffer from a largecommunication message overhead. The performance of such conventionalprotocols may be improved to a certain extent by improving sensing andcommunication reliability. However, this requires very careful andlaborious (expensive and time-consuming) configuration/commissioning ofthe sensors and the communication modules.

With radar sensors, for example, based on Doppler or FMCW (frequencymodulated continuous wave), it is possible to extract additional trafficinformation related to the detected object's velocities, within thesensing range of the sensor. Using such velocity information offers thepotential of improving dimming behavior in the OLN. However, the sensingis typically error-prone which may lead to missed detections and falsealarms. Further, the detected velocity may have limited accuracy. Forexample, the estimated velocity may be different from the actualvelocity within an uncertainty range. Moreover, communications linksacross light units/poles such as wireless links are error-prone (due tofading, shadowing conditions, etc.) and range-limited. In this regard,accurate communication is not guaranteed, but there is a probabilityassociated with communication between any two lighting units/poles beingsuccessful. Furthermore, received power degrades with distance and hencesuccessful communication may occur only up to a certain distance, whichis termed the communication range.

Accordingly, a need exists in the art for methods and protocols toaddress the shortcomings of the conventional protocols and conventionalOLN systems noted above.

It is one object of the present invention to present control methods fordetermining the dimming behavior of lighting units (LUs) in an OLN sothat the dimming performance is improved.

Another object of the present invention to present communicationprotocols for messaging between and among LUs in the OLN to meet orexceed required response performance.

Another object of the present invention is to improve the energy savingsin the OLN and/or reduce light pollution by providing appropriate lightlevels conforming to expected dimming behavior.

Another object of the present invention is to reduce the communicationmessage overhead between LUs.

One feature of the present invention is to use a lighting/dimmingcontrol protocol that uses the detected object's velocity to adapt theLU response range. In this regard, the response range can be consideredthe number of the LUs that should be turned “ON” or “OFF” based upon thedetection. For example, in the direction of the detected object, one ormore additional LUs should be turned “ON” when a first LU has detectedthe object. The response range can be selected based upon a distancefrom the first LU and/or a number of additional LUs (assuming a knownspacing between the additional LUs).

Another feature of the present invention is related to decision criteriato determine a “true detection” based on a local detection result, incombination with velocity detection results from neighboring lightingunits obtained by way of a control message.

It is noted that one conventional attempt to set a light level of alighting unit in dependence to a sensor determining a position andvelocity of an object is disclosed in EP2271184 A1. As understood byinventors, a master controller is described that communicates a dimmingcommand so that slave light sources can achieve an illumination profile.This reference, however, is not understood to disclose the distributedcommunication and control protocols described in the present inventionrelated to decision rules on when a control message should betransmitted, (ii) content of the communication message, and controlmessaging protocols with modes adapted to achieve a response rangedepending on object velocity, and (iii) designed decision rules at thelighting poles to decide dimming behavior. Moreover, the reference isunderstood to disclose that a current sensor detection result, incombination with previous sensor results and neighboring ones and/or thelight actuation results, can be used in a distributed way to decideillumination behavior.

Another feature of the present invention is related to a method toreduce communication overhead in the OLN using criteria for eachlighting unit to decide whether or not to send the control message toneighboring LUs.

In one embodiment, the present invention is directed to a method forcontrolling a plurality of lighting units in an outdoor lightingnetwork. The method includes the steps of detecting a vehicle within asensing range of the lighting unit and confirming that the detection istrue. If the detection is confirmed a response range is determined basedupon a velocity of the vehicle. One of several messaging protocols isthen selected based upon the determined response range and a controlmessage is sent, using the selected one messaging protocol, to otherselected lighting units to control a light level of the other lightingunits.

In another embodiment, the present invention directed to a method forcontrolling a light level output of a lighting unit in an outdoorlighting network. The method includes the steps of determining if thereis a true location detection and/or an ON control message is received bythe lighting unit. The true location detection is determined bydetecting an object within a sensing range of the lighting unit andconfirming the detection. The ON control message is determined byreceiving a control message from another lighting unit in the outdoorlighting network where the control message includes at least a list ofdestination lightings units, an ON/OFF control indication and a controlmessaging protocol mode designation. The received control message ischecked to determine if the identification code of the lighting unit isin the list of destination lighting units and if the ON/Off controlindication is ON which means that the control message is determined tobe the ON control message. The method also includes the step increasingthe light level output of the lighting unit based upon the determinationof the true location detection and/or the ON control message.

In yet another embodiment, the present invention relates to a method foran outdoor lighting network including a plurality of lighting units. Themethod includes the steps of detecting an object within a sensing rangeby at least one of the plurality of lighting units and determiningwhether to send a control message to one or more other lighting unitsbased upon status information related to the lighting unit from acurrent and past monitoring period and based upon status data from theone or more other of the plurality of lighting units. The method furtherincludes the step of sending the control message, based upon thedetermination, to one or more other of the plurality of lighting unitsto control the lighting in the outdoor lighting network.

In general, the various aspects, features and embodiments of the presentinvention may be combined and coupled in any way possible within thescope of the invention. The subject matter that is regarded as theinvention is particularly pointed out and distinctly claimed in theclaims at the conclusion of the specification.

The foregoing and other features and advantages of the invention will beapparent from the following detailed description taken in conjunctionwith the accompanying drawings.

FIG. 1 shows an outdoor lighting network 100 according to an embodimentof the invention.

FIG. 2 shows a control message diagram of according to an embodiment ofthe present invention.

FIG. 3 shows a control message decision diagram method according toanother embodiment of the invention.

FIG. 4 shows a control message decision diagram method according to yetanother embodiment of the invention.

As shown in FIG. 1, the outdoor lighting network 100 includes one ormore lighting units (1-8). The LUs (1-8) include a light producingmechanism 11, a sensor 12, a database 13, a communication interface 14and a light level controller 15.

In the forgoing description, reference will be made to neighbor andneighboring LUs (1-8). As an example, LU2 is the left neighbor of LU3and LU4 is the right neighbor of LU3.

The sensor 12 is used to detect one or more object(s) 20 along withtheir velocities (direction and speed) within a predetermined sensingrange. As noted above, the senor 12 may be any suitable sensor toachieve this result.

The communication interface 14 may be, for example, a hardwired linkand/or a wireless interface compatible with DSRC, 3G, LTE, WiFi, RFID,another type of wireless communication system and/or a visual lightcommunication. The communication interface 14 may be any suitablecommunication arrangement to transfer data between one or more of theLUs (1-8).

The database 13 need not be included in all of the LUs (1-8). Since theLUs (1-8) can communicate with one or more other LUs (1-8) and/or anintermediate node (not shown in FIG. 1), any data that would need to bestored or accessed by a particular LU (1-8) can be stored in andaccessed from the database 13 in another LU (1-8) or in the intermediatenode as needed.

The light level controller 15 is used to adapt the illumination outputof the light producing mechanism 11 based upon determinations made inresponse to detections of the object 20.

In operation, the LUs (1-8) within the outdoor lighting system 100perform various functions to manage lighting/dimming requirements asneeded.

However, before describing various methods, embodiments and protocols ofthe present invention, some notations, definitions and examples of dataformats are described below.

Below is an example memory format that may be used to store detectiondata from one of the LUs (1-8) and control message data from other LUs(1-10) in the database 13.

In each of the LUs (1-8), one or more of previous iterations (eachiteration is considered one monitoring period) of the detection data andstatus of the LU(s) (1-8) may be stored as shown in Tables 1 and 2. Thisdata and status may be stored in the database 13.

TABLE 1 local true local iteration detection detection velocitylight(on/off) i i-1 i-2 i-3

The monitoring period to be used will depend on the features and/orlocation of the OLN 100 and in consideration of the velocity of theobjects 20. For example, faster moving objects will require a smallermonitoring period to ensure proper detection as they move through thesensing range.

A stack of several entries (e.g., 10) may be used to store the data fromthe control messages from the other LUs (1-8) in the database 13 asshown in Table 2.

TABLE 2 LU_ID of Local iteration sender detection Velocity I n ON/OFF

As used hereinafter:

ld(i) denotes a local detection of the object 20 by one of the LUs (1-8)at iteration i;

true_ld(i) denotes a true local detection by the LU at iteration i;

ld(i)=1 means a local detection (i.e., the object 20 has been detectedby the sensor 12 at this particular LU) and ld(i)=0 means that theobject 20 has not been detected;

true_ld(i)=1 means a true local detection (i.e., the local detection hasbeen confirmed) and true_ld(i)=0 means that the local detection was notconfirmed;

light(i) denotes a light status of the LU;

light(i)=1 (or ON) means that the light producing mechanism 11 is turnedon (active) at iteration i, light(i)=0 (or OFF) means that the lightingproducing mechanism 11 is turned off (inactive or dimmed); and

v(i) denotes a velocity of the object 20 detected at iteration i.

In certain situations, as described below, it may be necessary todetermine that at least two of the objects 20 have a velocity that isthe same or close. For this purpose it can be declared that the twoobjects 20 with velocities v1 and v2, respectively, are the same orclose, if v1 and v2 have the same direction and|v1−v2|≦0.5 min(|v1|,|v2|).

In addition, in certain situations, it may be necessary to determinethat the velocity of the object 20 can be found from data obtained fromneighboring LUs (1-8) that is stored in the stack format describedabove). By traversing the stack data entries in the database 13, it canbe determined that the velocity of the object 20 can found from the dataobtained from neighboring LUs (1-8) if a stack entry satisfies all ofthe following four requirements:

-   -   1. The stack entry is an “ON” entry (a control message of remote        detection of ON is received from at least one of the neighboring        LUs (1-8) of the particular LU);    -   2. The entry is from the left or right neighboring LUs (1-8)        (depending on the direction of v(i));    -   3. v(i) and v(k) are close (where v(k) is the velocity in the        stack entry and k is the iteration number for that stack entry);        and    -   4. i-k is less than a limited period of iterations:        -   (e.g., round((inter-LU distance)/(abs(v(i))*T))+2, where T            is the monitoring period).

One final notation, the sensor 12 can only detect the velocity of theobject 20 but cannot detect the exact location of the object 20. In thisregard, when there is more than one of the object 20 in the sensingrange, if the velocities of the objects 20 are close, the sensor 12regards both the objects 20 as one object.

The method for deciding when the control message from one of the LUs(1-8) should be send to one or more other LUs (1-8) is now described.The decision method can be broken down into three parts:

-   -   Criterion to determine “true” local detection;    -   Criterion to send ON message; and    -   Criterion to send OFF message.

The criterion to determine the “true” local detection is to limit theeffects of a false detection by the sensor 12. When one of the LUs (1-8)has a local detection, the LU checks in the database 13 for the statusof the local detection, the status of light (on/off) in previousiterations and also the stack entries received from the other LUs (1-8)to decide if the local detection (i.e., confirm) is “true” or otherwisea false alarm. Given the local detection at iteration i, five cases mayoccur which need to be discussed.

Given ld(i)=1 (i.e., the object 20 has been detected in the sensingrange by the sensor 12 of the LU (1-8)):

-   -   i) If true_ld(i−1)=1, this likely means the LU (1-8) determines        a true local detection at previous iteration i−1, so that it is        determined/confirmed that: true_ld(i)=1;    -   ii) If true_ld(i−1)=0 and ld(i−1)=1 and light(i−1)=1, this        likely means there is a local detection at previous iteration        i−1 and the LU (1-8) decided to turn ON the light at iteration        i−1. However, the LU could not confirm ld(i−1) to be a true        local detection. If v(i) and v(i−1) are close, set true_ld(i)=1;        or if v(i) can be found from neighboring LUs (1-8), set        true_ld(i)=1.    -   iii) If true_ld(i−1)=0 and ld(i−1)=0, this could be due to the        object 20 just entering the sensing range of the LU (1-8). If        v(i) can be found from the neighbor LUs, true_ld(i)=1 is set.    -   iv) If the LU (1-8) is on the left end or on the right end of a        street then this LU (1-8) has neighbors only on one side and the        data in the stack entries is not complete for the determination        of a true local detection. To be conservative, true_ld(i)=1 is        set. It is noted that a grid map of all the LUs (1-8) in the OLN        can be used to identify location characteristics (e.g., end of        street) and other unique features of particular LUs (1-8).    -   v) Otherwise true_ld(i)=0 is set.

The ON message is sent by the LU (1-8) whose “true” local detection (asdescribed in the criterion to determine “true” local detection above) istrue_ld(i)=1. In the view of the LU_ID n, when there is a localdetection and it is a true local detection, if there is a “new” object20 that enters the sensing range of the sensor 12 (which means that thesensor 12 detects a new velocity that could not be found in the database13 of the LU (1-8)) then the LU sends the ON message to other LUs (1-8)within the response range.

To determine whether to send the ON message, two steps are performed bythe LU (1-8).

Step 1: First it is noted that the velocities (detected) in currentiteration i are denoted as V₁(i), V₂(i), . . . V_(n)(i). This example itis assumed that “n” velocities are detected in current iteration by thesensor 12. The velocities of previous iterations v(i−1) (assume “m”previous velocities) in the database 13 are traversed to determine ifthe first of the “n” current velocities is not close to any of theprevious “m” velocities in iteration i−1. If the first of the “n”current velocities is not found close then the first of the “n” currentvelocities is declared newly detected (i.e., arrived) and the ON messageis sent to the neighboring LUs (1-8). This is repeated for all “n” ofthe current velocities.

Step 2: If m>0 and n>m and in Step 1 the LU (1-8) does not send any ONmessages, this means there is a new object 20 (may be more than one) hasentered the sensing range of the LU (1-8) but the LU (1-8) does notrecognize the object 20 as newly detected. The reason is that thevelocity of the newly detected object 20 is close to the velocity in theprevious iteration i−1. In this case, the LU (1-8) regards two or moreof the objects 20 as the same object having the same velocity. In thiscase, the ON message is sent along with the largest velocity in currentiteration to LUs (1-8) in the response range.

Now the criterion to send the OFF message by the LU (1-8) is described.When the object 20 just leaves the sensing range of the LU (1-8) andthere is no other object 20 within the sensing range of the LU (1-8)(i.e. the local detection (ld(i)) of the LU (1-8) turns from 1 to 0),the LU (1-8) sends the OFF message which means that the local detection(ld(i) of the LU (1-8) is currently 0. The OFF message is sent to theneighboring LUs (1-8) in direction opposite to the direction of thevelocity of the object 20.

To determine whether to send an OFF message two steps are performed bythe LU (1-8).

Step 1: If ld(i)=0 and true_ld(i−1)=1 and light(i−1)=1, go to Step 2(which means that the LU (1-8) is not currently detecting the object 20by the sensor 12 but in the previous iteration there was a truedetection and the light was ON); otherwise do not send the OFF message;

Step 2: It is first noted that the velocity in iteration (i−1) isdenoted as v(i−1). By traversing the stack entries in the database 13,if v(i−1) can be found from the neighbors LUs (1-8) (see case 1 in theFIG. 2), the OFF message is sent to the neighboring LUs (1-8) in theopposite direction from which the object 20 is moving. If there are nomatches, do not send the OFF message.

In FIG. 2, the OFF message is sent at iterations i+1, i−2, i−5 bydifferent LUs (1-8). When the noted condition(s) are satisfied, each LU(1-8) sends the OFF message to the neighbors LUs in the directionopposite to the estimated direction of the object 20.

Next the control messaging protocol and message content within atransmission between/among LUs (1-8) is described. Three switch modesfor the control messaging protocol are disclosed:

-   -   Control messaging protocol mode 1;    -   Control messaging protocol mode 2; and    -   P2P protocol mode.

Control messaging protocol mode 1 is used for broadcasting/sending tomultiple destinations (i.e., LUs (1-8)) within a short response rangewhen there is less of a need to relay the same control message (packet)between the LUs (1-8) is required. Control messaging protocol mode 2 isused for broadcasting to multiple destinations within a larger responserange when there is more of a need to relay the same control message(packet) between the LUs (1-8) is required

The response range determines the need for relaying. A short responserange means that the control message is relayed to fewer destinations(i.e., LUs) and the furthest destination is close. A large responserange means the control message should be relayed to more destinationsand more relays are needed to send the control message to the furthestdestination.

P2P protocol mode is designed for point to point communication. Intypical OLN applications using such protocol modes, if the responserange of the LU (1-8) is within a radius of 40 meters, control messagingprotocol mode 1 may be used. If the response range of the LU (1-8) islarger than the radius of 40 meters, control messaging protocol mode 2may be used. If point to point communication is needed, P2P protocolmode may be used.

To determine the response range of the LUs, the velocity of the object20 must considered to adapt the response range accordingly. This may bedone, for example using a predetermined lookup table or algorithm. Table3 below is an example of a lookup table for the response range of theLUs (1-8).

TABLE 3 Velocity of the object # of LUs to be turned Response time 20(m/s) on: (back, front) (seconds) ≦4 (1, 1)  4-10 (1, 3) 8 10-20 (1, 4)5 20-30 (1, 6) 4.66 30-40 (1, 8) 4.5

The response time is the amount of time that a driver (of the object 20)needs to react upon seeing a situation at the furthest front LU (1-8)which is turned on. The response time is used to determine the number offront/forward LUs (1-8) (in second column of Table 3) that need to beturned on. This is to allow for a sufficient number of LUs (1-8) to turnon (i.e., light up) to provide visual comfort to the driver underdifferent velocity cases.Response Time=(LU spacing)*(number of front LUs)/(maximum velocity)

The Response Time can also be derived from the first two columns Table 3and for a given LU spacing.

A detailed description of each of the control messaging protocol modesis described below.

In the control messaging protocol mode 1 when the destination LU (1-8)receives the control message from the sending LU (1-8) an ACK is sentfrom the destination LU (1-8) to the sending LU (1-8).

Table 3 shows an example of the control message data format in a humanlanguage representation. It will be appreciated by one of ordinary skillin the art that this representation would be translated into a suitableformat for analog or digital transmission. In this example, the controlmessage is sent to the two left and right neighbor LUs (i.e., L1, 2 andR1, R2). However, it is noted that the control message can be sent tomore or less neighboring LUs (1-8) depending on the response rangeselected.

As noted above, if (front, back)=(2, 2) is designated to mean the lefttwo and right two neighbors of the LU (1-8) and if the LU_ID of the LU(1-8) with a local detection is n, the format of control message is asshown in Table 3.

TABLE 3 List of destination LUs L1, L2, R1,R2 Velocity (speed +direction) Lamp of local detection n content (local detection) ON/OFFSwitch mode of Control 1: Control messaging protocol mode 1; messagingprotocol 2: Control messaging protocol mode 2; 3: P2P protocol mode

In the control messaging protocol mode 1, the sender LU (1-8) sends thecontrol message (via the communication interface 14) to the list ofdestination LUs (1-8). The sender LU (1-8) stops sending when the ACK isreceived from all of the destination LUs (1-8). When the sender LU (1-8)receives the ACK from one of the destination LUs (1-8) that particulardestination LU (1-8) is not sent the control message again by the senderLU (1-8). This way only the destination LUs (1-8) that have not sent theACK would receive the repeat control messages from the sender LU (1-8).The sender LU (1-8) may re-send the control message to the destinationLUs (1-8) that have not sent an ACK a predetermined number of times,e.g., up to 4 times. This prevents an endless loop situation of one ofthe destination LUs (1-8) is not able to send the ACK.

When one of the destination LUs (1-8) receives the control message fromthe sender LU (1-8) (in this case the switch mode would be controlmessaging protocol mode=1), the destination LU (1-8) compares its ownLU_ID with the list of destination LUs (1-8). If a match is found thenthe following steps are performed:

Step 1: If an internal status flag has a value of less than two (whichmeans that this destination LU (1-8) has not replied with the ACK or hasreplied once but was not received by the sender LU (1-8)), go to Step 2;otherwise, if the internal status flag has a value of two, stop and donot send the ACK; and

Step 2: Increase the value of the internal status flag by 1, store thecontrol message and reply with the ACK to the sender LU (1-8).

When entering next iteration (monitoring period), the value of theinternal status flag is reset to zero.

Control messaging protocol mode 2 will now be described. In this mode,each of the LUs (1-8) on the destination list re-sends the controlmessage from the sender LU (1-8) twice without replying ACK to theoriginal sender LU (1-8). The control message contains the list ofdestination LUs (1-8). When one of the destination LUs (1-8) receivesthe control message, the destination LU (1-8) re-sends the controlmessage to its neighbors. The neighbor LUs (1-8), however, send the ACKback to the destination LU (1-8) that re-sent the control message.

By way of example, in the control messaging protocol mode 2, when thesender LU (1-8) has a local detection of the object 20 in its sensingregion, the LU (1-8) sends the control message to the LUs (1-8) on thelist of destination LUs (1-8). In this example, it is assumed that theLU_ID of the sender LU (1-8) with the local detection is n, and (front,back)=(6, 1) which means that the list destination LUs (1-8) would beL1, L2, L3, L4, L5, L6, R1 (the six left neighbors and one rightneighbor of the sender LU (1-8)). When one of the destination LUs (1-8)receives the control message from the sender LU (1-8) (in this case theswitch mode of control messaging protocol mode=2), the destination LU(1-8) compares its own LU_ID with the list of destination poles in thecontrol message. If there is a match, the destination LU performs thefollowing steps:

Step 1: If the internal status flag has a value of zero (which meansthat this destination LU (1-8) has not re-sent the control message toits neighbor LUs (1-8)), go to Step 2; otherwise, if the value of theinternal status flag is one, stop and do not re-send the controlmessage; and

Step 2: The destination LU (1-8) stores the control message, re-sendsthe control message two consecutive times to the neighboring LUs (1-8)and sets the value of the internal status flag to one (when enteringnext iteration (monitoring period), the value of the internal statusflag is reset to zero).

It is noted that in Step 2 above, the control message is sent twice toincrease the overall success rate of the communication by relaying,while still keeping the retransmission overhead minimal. However, twore-sends are not required and more or less re-sends can be used. Thenumber of re-send depends on the success rate of a single communicationand a requirement on overall success rate by relaying.

Step 3: If the value of the destination LU's LU_ID is different from thevalue of the LU_ID of the sender LU (1-8) by one (which means that thedestination LU (1-8) and the sender LU (1-8) are neighbors), reply withthe ACK to the sender LU (1-8).

If the sender LU (1-8) does not receive the ACK from two neighboring LUs(1-8) within the monitoring period, the P2P protocol mode is initiatedbetween the sender LU (1-8) and the neighboring LU (1-8) that did notreply with the ACK.

One advantage of the control messaging protocol mode 2 is that itensures fast communication to the furthest LU (1-8) within the responserange. The control messaging protocol mode 2 is also robust consideringthat the LUs (1-8) receive the control message from several neighbor LUs(1-8).

In another embodiment, the control messaging protocol mode 2 may alsoinclude an ACK (acknowledgement) mechanism between the original senderLU (1-8) and the destination LUs (1-8).

The control messaging protocol mode 2 can also be used for a dynamiccommunication range as shown in FIG. 3. FIG. 3 shows an example wherethe sender LU (in black) needs to send the control message to tenneighbor LUs. There are multiple routes of relaying the control messageto different destinations, which provides robustness of communication.

The P2P Protocol Mode will now be described. The P2P Protocol Mode maybe initiated in at least two situations:

Situation 1. In the control messaging protocol mode 2, the sender LU(1-8) (which is not the original sender LU (1-8) of the control messageas described above) does not receive the ACK from two neighboring LUs(1-8); and

Situation 2. When the status of the local detection of the LU (1-8)changes from ON to OFF, the LU (1-8) sends an OFF message to theneighboring LUs (1-8) which are in the reverse direction of the velocityof the object 20. The LU (1-8) stops sending the OFF message when the LU(1-8) receives all the ACKs from the destination LU (1-8). However, alimit may be sent on the number of times (e.g., 6 times) the LU (1-8)sends the OFF message even if all the ACKS are not received. Thisprevents an endless loop situation if for any reason one or more of thedestination LUs (1-8) cannot respond with the ACK.

Table 4 shows an example of the OFF message. In this example, the LU_IDof the sender LU (1-8) with a local detection is n and the velocity istaken from the database 13 from the previous iteration.

TABLE 4 List of destination LUs R1 Velocity(speed + direction) * Lamp oflocal detection n content (local detection) ON/OFF Switch mode ofControl 1: Control messaging protocol mode 1; messaging protocol 2:Control messaging protocol mode 2; 3: P2P protocol mode

When the destination LU (1-8) receives the control message that includesSwitch mode of Control messaging protocol mode=3, if the LU_ID of the LU(1-8) is on the list of destination LUs (1-8), the destination LU (1-8)performs the following steps:

Step 1: If the internal status flag has a value of less than two (whichmeans that this LU (1-8) has not re-sent the control message or hasreplied once with the ACK but the ACK was not received by the sender LU(1-8)), go to Step 2; otherwise, if the value of the internal statusflag is 2, stop and do not take further action;

Step 2: increase the value of the internal status flag by 1, store thecontrol message and reply to the sender LU (1-8) with the ACK (theinternal status flag is reset to zero in the next iteration, i.e.,monitoring period).

The decision rule for dimming/light level control for the LUs (1-8) inthe OLN will now be described. The following set of decision rules areemployed by the LUs (1-8):

(1) If local detection(i)=ON, then light(i)=ON;

(2). else if the ON message is received from one of the neighbor LUs(1-8) in current iteration i, then light(i)=ON;

(3). else if the OFF message is received in the current iteration i andall ON entries in the stack have been deactivated then light(i)=off(i.e., reset the light from ON to OFF);

(4). else if: local detection(i)=OFF and light(i−1)=ON and no OFFmessage is received in the current iteration i and all ON entries in thestack have been deactivated then light(i)=OFF (i.e., reset the lightfrom ON to OFF);

(5). else: light(i)=light(i−1) (keep the light status the same).

Cases (1) and (2) are two cases to set the light to be ON. Cases (3) and(4) are two cases to reset the light from ON to OFF. Case (5) includesall other cases that maintain the status of the light.

It is also noted that in the above example, the status of the LU (1-8)(light) is described as “ON” or “OFF.” However, it should be understoodthat “OFF” means that the light level from the light producing mechanism11 is reduced from the light level when the light producing mechanism 11in the “ON” state. For example, in the “ON” state, the light level maybe full power.

Testing results will now be described comparing embodiments of thepresent invention with a conventional method for dimming/controlling theLUs (1-8). In this test comparison, the following system parameters havebeen used:

(1) number of iterations: m=5000 times;

(2) number of LUs: n=80 with the LUs arranged along on one side of astraight road;

(3) period T=0.25 seconds (i.e., the monitoring period);

(4) inter-LU distance apart=20 m;

(5) success probability for a single communication between two of theLUs within communication range=0.8 (i.e., 80%);

(6) sensing range of the LUs (1-8): radius=15 m;

(7) miss detection probability of a local detection=0.05 (i.e., 5%);

(8) false alarm probability of a local detection=0.05 (i.e., 5%);

(9) traffic mode: Busy mode. On average, every time there are sevenvehicles (i.e., the objects 20) on the road of 80 LUs (1-8);

(10) communication range of the LUs (1-8): radius <=40 m;

(11) response range of the LUs (1-8) based on the velocity of thevehicle (see look up Table 5 below); and

TABLE 5 Velocity # of LUs to be turned Response time (m/s) on :(back,front) (seconds) ≦4 (1, 1)  4-10 (1, 3) 8 10-20 (1, 4) 5 20-30 (1, 6)4.66 30-40 (1, 8) 4.5

(12) uncertainty of detection of the velocity of vehicle: +/−20%. Inthis test example, it is assumed that the actual velocity is Va, then,the detected velocity Vdε(0.8 Va, 1.2 Va) with a probability of uniformdistribution.

It is noted that with the monitoring period of 1=0.25 and 5000iterations, the total time to complete the test was 1250 seconds.

Embodiments of the present invention are compared with the conventionalmethod for dimming/controlling the LUs (1-8) on the basis of fourperformance metrics:

1). Type-I Error Rate: a/b

“a” are situations in which the LU (1-8) is turned OFF but one or morethe objects 20 appear within the response region of the LU (1-8); andwhere “b” is defined as m*n (m is the number of iterations and n is thetotal number of the LUs).

2). Type-II Error Rate: a/b

For type II errors, “a” are situations in which the LU (1-8) is turnedON but no object 20 appears within the response region of the LU (1-8).It is noted that for calculation of the type II errors, the three LUs onleft end and the three LUs on right end of the street are not accounteddue to an end effect. “b” is defined as m*(n−2*3).

3). Energy Percentage of Non-Control Energy Cost: a/b*100%

For this performance metric, “a” is the number of the LUs (1-8) thathave been turned ON throughout all the iterations and where “b” isdefined as m*n. For “b,” this assumes that all the LUs (1-8) are turnedON all the time.

4). The Total Number of Sent Control Messages by all the LUs (1-8).

In this test comparison, the velocities of the vehicles (i.e., theobjects 20) are generated by following a normal distribution with themean value 18 m/s and standard deviation of seven. This means that theaverage response range, i.e. the average number of response LUs (1-8)when a local detection occurs is about six (e.g., it would be five forspeeds in the range of 20-30 m/s and seven for speeds in the range of30-40 m/s).

For the conventional method for dimming/controlling the LUs (1-8), tworesponse standards are used in the test comparison. The first responsestandard is to turn ON the left three and right three LUs (1-8) if alocal detection occurs. The second response standard is to follow thesame lookup Table 5 as described above in connection with variousembodiments of the present invention.

As can be seen by the summary in Table 6 below, embodiments of thepresent invention have better performance in all four performancemetrics.

TABLE 6 Embodiment of Conventional Conventional present invention methodmethod Lookup Table 5 of Response Lookup Table of relation of responserange of left 3 relation of response Response standard range andvelocity and right 3 poles range and velocity Results Type-I error rate0.0582% 0.7100% 4.4900% Type-II error rate  4.470%  18.26%  8.12% Energypercent of 37.920%  55.64%  37.28% non-control energy cost Total sentmessages 94278 800000 910540 Total ACK messages 29701 0 0

In yet another embodiment, control rules and methods are described basedupon binary detection sensing. The decision criterion for sending thecontrol message will first be described. In this embodiment, The LU(1-8) sends only a ‘local detection’ (Id) control message and notransmission occurs if no object 20 is detected by the LU (1-8). Toimprove the likelihood that the local detection is valid, the followingcriteria are used.

Given a local detection, there are three cases in which the controlmessage is transmitted, i.e. an ON message is sent from that LU. In thefollowing,

(indicates checking of a detection the object 20 either remotely orlocally)

(indicates a local detection of the object 20 or remote detection isfound)

If there is one or more red boxes in a region of blue boxes, the localdetection at iteration i is a “True” local detection.

If any one of the following three cases is satisfied (indicating thatthe local detection is a “True” local detection), then send the controlmessage (i.e., the ON message) to neighbor LUs (1-8), i.e. if “True”local detection=1, broadcast ON message to neighbor LUs (1-8).

-   -   1) If ld(local detection)(i)=1, ld(i−1)=1, then first, check        local detections for iterations from i−2 to i−3. Either        ld(i−2)=1 occurs, or else ld(i−2)=0 and ld(i−3)=1, in which case        it is likely that the object 20 (e.g., a vehicle) stays within        the sensing range of the LU for a period of time and only one        miss detection at iteration i−2.

If no local detection at iteration i−2 and i−3, check neighbor LUs (L1and R1) for iterations from i−2 to i−3. This situation likely indicatesthat, with a high probability, the object 20 has just arrived at the LU(Id) at iteration i−1 (ld(i−1)=1) from L1 (first left neighboring LU) orR1 (first right neighboring LU).

-   -   2) If ld(i)=1, ld(i−1)=0, check local detections for iterations        from i−2 to i−3. If ld(i−2)=1 or ld(i−3)=1, ld(i−1)=0 is a        likely missed detection.        -   If no local detection is found, check remote detection from            L1 and R1 for iterations from i−1 to i−3. It there is a            remote detection, it is likely that a vehicle just arrived            at the LU (Id) at iteration i (ld(i)=1) from L1 (first left            neighboring LU) or R1 (first right neighboring LU).

-   -   3) If the LU of left end or right end on the street has a local        detection, it broadcasts the ON message. This is for the case        that the object 20 enters from an end of the street where LUs        (1-8) have neighbors only on one side of the street.

If at least one of the above conditions are met then the control messageis one or more times. It is preferred that the control message isbroadcast twice to improve the likelihood of proper reception by thereceiving LUs (1-8). The control message contains a list of LUs that aredestinations (i.e., the receiving LUs (1-8)). See Table 7 below for anexample format of the control message in this embodiment. In thisexample, If LU_ID of the LU (1-8) with the local detection is n and theresponse range is R=3 then the control message has the following format:

List of destination LUs L1, L2, L3, R1, R2, R3 LU of local detection Ncontent (local detection) ON

When a particular LU (1-8) has a local detection of the object 20 in itssensing region, the LU (1-8) broadcasts the control message to all LUs(1-8) in the list of destination LUs. When one or more LUs (1-8) receivethe control message, the receiving LU(s) (1-8) compares its own LU_IDwith the list of destination LUs. It the receiving LU(s) 1-8) are on thelist of destination LUs, the following steps are performed:

Step 1: If the internal status flag is 0 (i.e., the control message hasnot been resent yet), go to Step 2; otherwise, if the internal statusflag is 1, stop and do not resend the control message; and

Step 2: stores the control message, resent the control message(preferably two consecutive times) and set the internal status flag to 1(when entering the next monitoring period, the internal status flag isreset to 0).

The decision rule for dimming/light level control for the LUs (1-8) inthis embodiment now be described. The following set of decision rulesare employed by the LUs (1-8):

-   -   (1) If: local detection(i)=ON then light(i)=on;    -   (2) else if: the control message (i.e., the ON message) is        received from a neighbor LU (1-8) in current iteration I then        light(i)=on;    -   (3) else if: there is no local detection and remote detection        (the ON message received from left three or right three neighbor        LU (depending on the response range)) in three consecutive times        (for iteration i, i−1, i−2) and light(i−1)=on then light(i)=off        (reset the LU (1-8) from ON to OFF);    -   (4) else if: no local detection and remote detection in        iteration i and i−1 but at iteration i−2 there is a remote        detection from neighboring L3 (the third left LU (1-8)) or R3        (the third right LU (1-8)) then light(i)=off (reset the LU (1-8)        from ON to OFF); and    -   (5) else: light(i)=Light(i−1) (LU (1-8) status stays the same).

Cases (1) and (2) above are two cases to set the LU (1-9) to be ON andCases (3) and (4) are two cases to reset the LU (1-8) from ON to OFF.Case (5) includes all the other cases that maintain the status of the LU(1-8).

One advantage of this embodiment is that it ensures fast communicationto the furthest LU (1-8) within the response range. It is further robustdue to the fact that the LU (1-8) receives control message from severalneighbor LUs (1-8). The embodiment may be further made robust byintroducing an optional ACK (acknowledgement) mechanism, wherein asuccessful transmission is ACKed by the receiving LU (1-8). It canfurther be adapted to a dynamic communication range as shown in FIG. 4.

Testing results for this embodiment will now be described comparingembodiments of the present invention with a conventional method fordimming/controlling the LUs (1-8). In the test comparison for thisembodiment, the same system parameters (1)-(10) have been used as notedabove. System parameters (11) and (12) have been replaced with:

(11a) Response range of LUs (1-8): Radius=60 m, i.e. left three andright three LUs (when there is the object 20 within the sensing range ofthe LU, the left three and right three LUs (1-8) should be turned ON).

The same four performance metrics are used as in the previous testcomparison.

In this test comparison, two cases for the reference protocol areconsidered. In the first case, the probability of successfulcommunication=0.8, probability of missed detection=0.05 and probabilityof false alarm=0.05. In the second case, the probability of successfulcommunication=0.9, probability of missed detection=0.01 and probabilityof false alarm=0.05. The second case corresponds to a situation wherecommunication sensing reliability has been improved by carefulconfiguration/commissioning. For the reference protocol, the controlmessage is broadcast two times (a similar comparison with the embodimentof the present invention) and also that the response range is R=3(again, so that the response range comparison is maintained). Inpractice, this is a deficiency of the reference protocol in that itcannot guarantee a response range.

As can be seen by the summary in Table 8 below, embodiments of thepresent invention have better performance in all four performancemetrics.

TABLE 8 Embodiment of Reference Reference the present algorithm[1]algorithm[2] invention Param- Communication 0.8 0.9 0.8 eters successprobabil- ity Miss detection 0.05 0.01 0.05 False alarm 0.05 0.05 0.05Results Type-I error rate 0.7100% 0.1400% 0.0502% Type-II error rate 18.26%  18.27%  2.48% Percentage of  54.64%  56.22%  40.77% non-controlenergy cost Total sent 8.00E+05 8.00E+05 5.153E+05 messages

The foregoing detailed description has set forth a few of the many formsthat the invention can take. The above examples are merely illustrativeof several possible embodiments of various aspects of the presentinvention, wherein equivalent alterations and/or modifications willoccur to others skilled in the art upon reading and understanding of thepresent invention and the annexed drawings. In particular, regard to thevarious functions performed by the above described components (devices,systems, and the like), the terms (including a reference to a “means”)used to describe such components are intended to correspond, unlessotherwise indicated to any component, such as hardware or combinationsthereof, which performs the specified function of the describedcomponent (i.e., that is functionally equivalent), even though notstructurally equivalent to the disclosed structure which performs thefunction in the illustrated implementations of the disclosure.

The principles of the present invention are implemented as anycombination of hardware, firmware and software. Moreover, the softwareis preferably implemented as an application program tangibly embodied ona program storage unit or computer readable storage medium consisting ofparts, or of certain devices and/or a combination of devices. Theapplication program may be uploaded to, and executed by, a machinecomprising any suitable architecture. For example, the LUs (1-10) may beimplemented on a computer platform having hardware such as one or morecentral processing units (“CPUs”), a memory, and input/outputinterfaces. The computer platform may also include an operating systemand microinstruction code. The various processes and functions describedherein may be either part of the microinstruction code or part of theapplication program, or any combination thereof, which may be executedby a CPU, whether or not such computer or processor is explicitly shown.In addition, various other peripheral units may be connected to thecomputer platform such as an additional data storage unit and a printingunit.

Although a particular feature of the present invention may have beenillustrated and/or described with respect to only one of severalimplementations, such feature may be combined with one or more otherfeatures of the other implementations as may be desired and advantageousfor any given or particular application. Furthermore, references tosingular components or items are intended, unless otherwise specified,to encompass two or more such components or items. Also, to the extentthat the terms “including”, “includes”, “having”, “has”, “with”, orvariants thereof are used in the detailed description and/or in theclaims, such terms are intended to be inclusive in a manner similar tothe term “comprising”.

The present invention has been described with reference to the preferredembodiments. However, modifications and alterations will occur to othersupon reading and understanding the preceding detailed description. It isintended that the present invention be construed as including all suchmodifications and alterations. It is only the claims, including allequivalents that are intended to define the scope of the presentinvention.

The invention claimed is:
 1. A method for controlling a plurality oflighting units in an outdoor lighting network, the method comprising thesteps of: detecting at least one object within a sensing range by atleast one of the plurality of lighting units); dynamically determining aresponse range based upon a velocity of the as least one object afterdetection; confirming if the detection of the at least one object istrue by checking a previous local detection status and/or a previouslight level status of the at least one of the plurality of lightingunits and/or status data received from others of the plurality oflighting units to confirm if the detection of the at least one object istrue; selecting one of a plurality of messaging protocols based upon thedetermined response range; and sending a control message, using theselected one messaging protocol, to another one or more of the pluralityof lighting units to control a light level of the another one or more ofthe plurality of lighting units.
 2. A method for controlling a pluralityof lighting units in an outdoor lighting network, the method comprisingthe steps of: detecting at least one object within a sensing range by atleast one of the plurality of lighting units); dynamically determining aresponse range based upon a velocity of the as least one object afterdetection; selecting one of a plurality of messaging protocols basedupon the determined response range; sending a control message, using theselected one messaging protocol, to another one or more of the pluralityof lighting units to control a light level of the another one or more ofthe plurality of lighting units; and wherein the determining theresponse range step includes selecting the response range using thevelocities of two or more objects to adapt the respective response rangefor each object.
 3. The method according to claim 2, wherein theselecting one of a plurality of messaging protocols step includesselecting a first protocol when the response range is a first range andselecting a second protocol when the response range is a second rangethat is larger than the first range.
 4. The method according to claim 3,wherein the selecting one of a plurality of messaging protocols stepfurther includes selecting a third protocol when a predeterminedcondition is not met while in the second protocol.
 5. The methodaccording to claim 3, wherein the selecting one of a plurality ofmessaging protocols step further includes selecting the third protocolto send a second type of control message to reduce the light level ofthe another one or more of the plurality of lighting units.
 6. A methodfor controlling a light level output of a lighting unit in an outdoorlighting network, the method comprising the steps of: determining ifthere is a true location detection and/or an ON control message isreceived by the lighting unit where; determining the true locationdetection includes the steps of detecting an object within a sensingrange of the lighting unit and confirming that the detection of theobject is true; determining the ON control message includes the stepsreceiving a control message from another lighting unit in the outdoorlighting network, wherein the control message includes at least a listof destination lightings units, an ON/OFF control indication and acontrol messaging protocol mode, checking if an identification code ofthe lighting unit is in the list of destination lighting units and ifthe ON/Off control indication is ON which means that the control messageis determined to be the ON control message; and increasing the lightlevel output of the lighting unit based upon the determination of thetrue location detection and/or the ON control message.
 7. The methodaccording to claim 6, further comprising the step of sending the ONcontrol message to at least one other lighting unit if the light levelout of the lighting unit is increased in the increasing step.
 8. Themethod according to claim 6, further comprising the steps of:determining if at least one of two OFF conditions have been met by thelighting unit: determining the first OFF condition includes the steps ofreceiving an OFF message in a current monitoring period and verifyingthat the OFF control message was received by the lighting unit from anyother lighting unit that had previously send the ON control message tothe lighting unit; determining the second OFF condition includes thesteps of determining that there no true local detection by the lightingunit verifying that the light level of the lighting unit was increasedin a previous monitoring period and that in the current monitoringperiod the lighting unit the OFF control message was received from anyother lighting unit that had previously send the ON control message tothe lighting unit; and reducing the light level output of the lightingunit based upon the determination of the first and/or second OFFcondition.
 9. The method according to claim 6, wherein the step toconfirm that the detection of the object is true includes checking aprior detection status and/or a prior light level status of the lightingunit from previous monitoring period and/or status data received fromone or more other lighting units in the outdoor lighting network toconfirm if the detection of the at least one object is true.
 10. Themethod according to claim 9, wherein the status data received from theone or more other lighting units includes an indication of the previousmonitoring period, an identification code for the other lighting unit,an ON/OFF status indication and information on a velocity of the object.11. A method for an outdoor lighting network including a plurality oflighting units, the method comprising the steps of: detecting at leastone object within a sensing range by at least one of the plurality oflighting units; determining whether to send a control message to one ormore other of the plurality of lighting units based upon statusinformation related to the lighting unit from a current and a pastmonitoring period and/or based upon control data from the one or moreother of the plurality of lighting units; and selecting one of aplurality of messaging protocols based upon a response range, theresponse range being based upon at least one velocity of the at leastone object; and sending the control message using the selected messagingprotocol, to the one or more other of the plurality of lighting units tocontrol lighting in the outdoor lighting network.
 12. The methodaccording to claim 11, wherein, if there are two or more objects, thedetermining step includes the step of traversing two or more velocitiesof the objects and if one or more of the velocities is determined to bea new velocity, sending the control message.
 13. The method according toclaim 12, wherein in the determining step if a first velocity of the atleast one object is considered close to second velocity already detectedfrom another object, sending the control message with the first orsecond velocity depending on which is larger.
 14. The method accordingto claim 11, wherein the control message include a list of the one ormore other of the plurality of lighting units intended to receive thecontrol message, velocity information of the at least one object, statusinformation of the at least one of the plurality of lighting units. 15.The method according to claim 14, wherein the determining step furtherincludes selecting the list of the one or more other of the plurality oflighting units based upon a response range that is adapted in accordancewith a velocity of the at least one object.
 16. The method according toclaim 11, wherein in the determining step first checks if the localdetection in the current and an immediately previous past monitoringperiod by the at least one of the plurality of lighting units thatdetected the object, if yes then checks if the local detection was alsomade in another past monitoring period, and if yes, it is determined tosend the control message.
 17. The method according to claim 16, whereinif the determining step there is no local detection in the another pastmonitoring period, the control data from the one or more other of theplurality of lighting units is checked if the object was detected in theanother past monitoring period by the one or more other of the pluralityof lighting units and if the object was detected, it is determined tosend the control message.
 18. The method according to claim 11, whereinin the determining step first checks if the local detection in thecurrent and not in an immediately previous past monitoring period by theat least one of the plurality of lighting units that detected theobject, if yes then checks if the local detection was also made inanother past monitoring period, and if yes, it is determined to send thecontrol message.
 19. The method according to claim 18, wherein if thedetermining step there is no local detection in the another pastmonitoring period, the control data from the one or more other of theplurality of lighting units is checked if the object was detected in theimmediately previous past monitoring period or the another pastmonitoring period by the one or more other of the plurality of lightingunits and if the object was detected, it is determined to send thecontrol message.